The present invention relates to the field of solar cell manufacturing, and particularly to a reaction apparatus and method for manufacturing a CIGS-based absorber of a thin film solar cell.
In recent years, people increasingly pay attention to issues of energy and environment, and the nuclear energy and the solar energy are the most prospective new energies to be developed. However, since nuclear leakage occurred in Japan, people begin to realize that the solar energy is the safest and the most environment-friendly new energy. A solar cell can directly convert sunlight into the electric energy. A solar cell is made of a semiconductor, and basically, when the sunlight irradiates the solar cell, a part of the sunlight is absorbed in the semiconductor material. Through a p-type semiconductor and an n-type semiconductor in the semiconductor material, electrons (negative) and electron holes (positive) are generated. The electrons are separated from the electron holes to form a voltage drop, and the energy stimulates the electrons to get rid of the constraint, so that the electrons flow freely. One or more electric fields exist in each solar cell, and an electron beam may be forcedly absorbed, released and flow in a certain direction. This electron beam current may be collected to the top and the bottom of a solar cell through metal contact, and then transmitted to a load through a lead. It means that the absorbed sunlight energy is converted into the semiconductor energy. Meanwhile, the current magnitude together with the voltage generated by the built-in electric field of the solar cell embodies the capacity of the solar cell.
In the conventional solar cell manufacturing, silicon is used as a monocrystal or polycrystal silicon chip which may absorb light. A wafer undergoes several process steps, and then is integrated to a module. The material and process costs of a crystalline silicon solar cell are high, so the manufacturing cost of a solar cell module is high. The technology of the thin film solar cell is greatly developed in the past thirty years, and the manufacturing cost thereof is lower than that of the crystalline silicon solar cell. Generally, the thickness of the semiconductor absorbing layer of the thin film solar cell is less than 1% of the thickness of the absorbing layer of the crystalline silicon cell, and the absorbing layer of the thin film solar cell is deposited on a substrate material with a relatively low cost, which is applicable to low-cost and mass production.
After development and evolution of the first generation monocrystal silicon solar cell, the second generation polycrystal silicon solar cell, and the non-crystalline silicon solar cell, the third generation thin film solar photovoltaic cell emerges. The CIGS-based thin film solar cell (a compound semiconductor formed of copper, indium, gallium, and selenium, and named as CIGS by taking initial letters of the four components) has advantages such as high light absorbing coefficient, high conversion efficiency, adjustable band gap, high stability, and strong anti-radiation capability, and is highlighted widely. In a lab, the conversion efficiency is up to more than 20%, and even the thin film with the thickness being 1 μm may obtain enormous electric energy production, so the CIGS-based thin film solar cell is currently a thin film photovoltaic cell with the highest conversion efficiency, and is honored by the industry as: a rising star of solar cell products.
The CIGS thin film is a composite semiconductor material as an absorber for absorbing sunlight, and includes some group-IB (copper, silver, and gold), group-IIIA (boron, aluminum, gallium, indium, and titanium) and group-VIA (oxygen, sulfur, selenium, tellurium, and polonium) elements.
However, existing reaction apparatus for preparation of the CIGS-based absorber often leads to poor stability of concentration and pressure of the gas in the reaction chamber, resulting in an uneven distribution of a CIGS thin film absorber material, substantially lower fabrication yield, and poorer energy conversion performance of the CIGS-based thin film solar cell. All these issues are adverse to mass production and popularization of the CIGS-based thin film solar technology.
From the above, it is seen that an improved apparatus and method for forming a CIGS absorber material in an reactive process is desired.